Stable isotope tracer methodology enables in vivo quantification of acute responses of metabolic pathways. In many previous studies we have shown that the results of metabolic studies with stable isotopes have accurately predicted long-term outcomes of nutritional therapies. A primary goal of this core will be to support metabolic research utilizing stable isotope methodology throughout the scientific community. Support of stable isotope tracer studies will include sample and data analysis, and training. We will also continue to develop new methodologies as needed to support these studies. In addition, we will actively train investigators on stable isotope tracer methodology. Finally, we will seek to extend collaborations throughout the world to develop a market for our analytical services and to provide for continued financial support. The core will prioritize stable isotope analyses for NIH-funded projects;however, any investigator utilizing stable isotope methodology may request analytical services. The PI is an experienced and well respected researcher in stable isotope methodology who moved from the UTMB and Shriners to University Arkansas and is receiving excellent support from the university. The aims of this project are to provide analytical support for research grants utilizing stable isotope methodology;to develop new methods to support studies of metabolic processes;to educate the scientific community regarding the in vivo applications of tracer methodology using stable isotopes in human subjects;and enhance collaborations to develop a clientele for continued financial support. Project Narrative: This proposal describes a stable isotope analytical core to support world-wide research in human metabolic studies. The core offers routine and specialized sample analysis on a minimal fee-for-service basis. In addition, it will provide assistance in methods development and training in the use of stable isotopes in human metabolic studies.